1. Field
This disclosure relates generally to phase locked loops, and more specifically, to phase locked loops with burn-in mode.
2. Related Art
Phase locked loops (PLLs) are very important for controlling clock frequency which is a significant consideration for processors and other circuits operating at high frequencies. PLLs present an inherent difficulty in they are mostly analog in operation in an environment that has mostly digital circuits. Furthermore, during burn-in, in which the logic circuits outside the PLL are stressed by elevated voltages and temperatures, the PLL is typically deactivated by grounding its power supplies so as not to be damaged by the burn-in process. Since the PLL is deactivated, none of the analog or digital circuits are stressed during burn-in. However, it is desirable to include the PLL circuitry during the burn-in process in order to obtain improved burn-in coverage and screen out bad parts due to PLL related failures.